Republican presidential candidates are weighing in on controversial comments made about Muslims. Here's what they're saying. (The Washington Post)

A lot of people are expressing shock today that presidential candidate Ben Carson said over the weekend that no Muslim should be elected president. But anyone who has been following conservative politics in recent years, or who knows much about Carson, wouldn’t have been shocked at all. The truth is that Carson is immersed in a part of the conservative movement that rejects some fundamental American values. It’s not a small part of that movement, and it’s worth understanding.

To be clear, I’m not talking about all conservatives or all Republicans. There is a significant split within the movement and the party, which one can see in the reaction to Carson’s comments, just as we did in reaction to Kentucky county clerk Kim Davis’ efforts to prevent gay people from being legally married in her county. In both cases, one group of people, including some presidential candidates, arrived at their position through their understanding of essential American principles, while the other group believes that Christians in particular should occupy a privileged place in law and society (granting that a few years ago they started citing “Judeo-Christian” values, making Jews sort of the equipment manager for the Christian spiritual varsity squad).

It may sound like an unfair criticism to say they’ve rejected foundational principles, but stay with me while I explain. To begin, let’s look at what Carson said on “Meet the Press” yesterday when Chuck Todd asked him whether a president’s faith should matter:

CARSON: Well, I guess it depends on what that faith is. If it’s inconsistent with the values and principles of America, then of course it should matter. But if it fits within the realm of America and consistent with the constitution, no problem.

TODD: So do you believe that Islam is consistent with the constitution?

CARSON: No, I don’t, I do not.

TODD: So you —

CARSON: I would not advocate that we put a Muslim in charge of this nation. I absolutely would not agree with that.

Given the chance to clarify later, Carson didn’t back off a bit:

In an interview with The Hill, Carson opened up about why he believes a Muslim would be unfit to serve as commander in chief.

“I do not believe Sharia is consistent with the Constitution of this country,” Carson said. “Muslims feel that their religion is very much a part of your public life and what you do as a public official, and that’s inconsistent with our principles and our Constitution.”

Carson said that the only exception he’d make would be if the Muslim running for office “publicly rejected all the tenants of Sharia and lived a life consistent with that.”

“Then I wouldn’t have any problem,” he said.

For the record, the word “sharia” simply means “law” in Arabic. But Carson’s dime-store understanding of Islam probably comes from the likes of Glenn Beck, who regularly tells his listeners that sharia is coming to America, I suppose because the Taliban are going to take over your local city council and replace existing law with somebody’s interpretation of Islam. All over the country, but particularly in the South, there are public officials who try to pass laws to fight the imaginary threat of “creeping sharia.”

Carson’s understanding of the Constitution seems strikingly weak, particularly Article 6, which states that “no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.” Carson would institute a religious test for the presidency — but only for Muslims, who would be required to “publicly reject” some imagined “tenets of sharia.” Of course, Carson does not say that Christians should have to make a public declaration that they would not impose their sectarian beliefs on the country in order to serve as president.

The point here isn’t just that Ben Carson’s views are extreme and unsettling, though they most certainly are (and not only on this question). They also bring together two strains running through conservatism in recent years: an often vitriolic Islamophobia, and the belief that the United States is and always has been of, by, and for Christians, with everyone else accorded a kind of ever-so-slightly inferior status. These ideas are commonplace in conservative media and in evangelical circles, and the most prominent pseudo-historian of that movement, David Barton, regularly advises prominent Republican politicians on the exalted place of Christianity in American history.

The idea of Christian supremacy in America is also fed by a campaign in which virtually all Republicans have participated in the last few years, the one that says that Christians are increasingly oppressed as America becomes more inclusive. In its most comical version, it’s manifested in Fox News’ annual “War on Christmas” extravaganza, where the fact that many department stores put up signs reading “Happy Holidays” instead of “Merry Christmas” is presented as a ghastly act of anti-Christian brutality (I’m not exaggerating — that’s actually what they say).

There’s a straight line between the War on Christmas and Ben Carson’s belief that Muslims should be excluded from the presidency, and it has to do with the decline of Christian hegemony in America. Fifty years ago, nobody worried about what department store signs said and nobody asked whether a Muslim could be president. The fact that Christmas was a national holiday, not a sectarian one, was so obvious almost no one would think to question it, any more than anyone would question the idea that of course every president would be a Christian. But over time, as American diversity has grown, a lot of unquestioned ideas like those have been brought into question. So department stores decide to be inclusive, putting up signs that send a friendly message to everybody, not just Christians. And though we haven’t had our first Jewish or Muslim or Hindu or non-theist president, we’ve reached the point where we can at least acknowledge it as a possibility.

But if you’re part of the group whose beliefs, traditions, and ideas were for so long taken as the default under which everyone had to live, that inclusiveness feels like a loss of privilege, which can easily be turned into the feeling that you’re under attack.

To repeat, there is a split within the Republican Party over this question. When the Kim Davis story broke, a number of GOP candidates — including Ted Cruz, Mike Huckabee, and yes, Ben Carson — took Davis’ side, agreeing that because she’s a Christian, she has the right to impose her views of marriage on an entire county, no matter what the Supreme Court says. Just try to imagine what they would have said if she were a Muslim refusing to grant a marriage license to any couple if the woman refused to wear a hijab.

On the other hand, other candidates — including Jeb Bush, Lindsey Graham, and Carly Fiorina — said that as a public official, Davis had to follow the law. A similar divide can be seen when it come to the growing Islamic-American population. George W. Bush repeatedly took pains to emphasize that America was not at war with Islam, and his former speechwriter Michael Gerson has spoken out emphatically against Islamophobia in their party.

Perhaps Ben Carson had never thought until recently about the possibility of a Muslim president, a thought he obviously finds disturbing. But he and those who agree with him are making increasingly clear that no matter how often they praise the Constitution and “American values,” their particular views of that document and those values are not what you might think.

The whole point of the  Bill of Rights is that it says everyone who is accused of a crime deserves a fair trial, even if the government thinks they’re guilty. It said that everyone gets to practice their religion, even if it’s not the religion of the government or the majority. It said that everyone has the right to be free of unreasonable searches and seizures, no matter who they are.

Of course, there were limits on the way those noble principles were put into practice, particularly when it came to those who were enslaved, but also to women, members of minority religions, and those with unpopular ideas. But America’s evolution in the time since is in large part a story of the widening of the circle of freedom to include more and more people. But to some, freedom’s widening circle isn’t an inspiration, it’s a problem.

Your devotion to ideas like liberty is tested when you have to apply them not just to yourself and people you think are like you, but to everyone — when you have to ask whether you believe in freedom of speech enough to allow books you disagree with, or whether you believe in freedom of religion enough to give all the same rights you have to people whose religious beliefs are different from yours. That’s a test that Ben Carson, and a troublingly large number of people in his party, continue to fail.